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Date: Mon, 19 Mar 2007 00:42:34 +0200 From: "Michael S. Tsirkin" <mst@....mellanox.co.il> To: "Michael S. Tsirkin" <mst@....mellanox.co.il> Cc: "Eric W. Biederman" <ebiederman@...i.com>, Alexey Kuznetsov <kuznet@....inr.ac.ru>, netdev@...r.kernel.org, Linux Kernel Mailing List <linux-kernel@...r.kernel.org>, general@...ts.openfabrics.org Subject: Re: [ofa-general] Re: dst_ifdown breaks infiniband? > Quoting Michael S. Tsirkin <mst@....mellanox.co.il>: > Subject: Re: [ofa-general] Re: dst_ifdown breaks infiniband? > > > Quoting Eric W. Biederman <ebiederman@...i.com>: > > Subject: Re: [ofa-general] Re: dst_ifdown breaks infiniband? > > > > "Michael S. Tsirkin" <mst@....mellanox.co.il> writes: > > > > >> > Why is neighbour->dev changed here? > > >> > > >> It holds reference to device and prevents its destruction. > > >> If dst is held somewhere, we cannot destroy the device and deadlock > > >> while unregister. > > > > > > BTW, can this ever happen for the loopback device itself? > > > Is it ever unregistered? > > > > Well I don't think the loopback device is currently but as soon > > as we get network namespace support we will have multiple loopback > > devices and they will get unregistered when we remove the network > > namespace. > > Hmm. Then the code moving dst->dev to point to the loopback > device will have to be fixed too. I'll post a patch a bit later. Does this look sane (untested)? Signed-off-by: Michael S. Tsirkin <mst@....mellanox.co.il> diff --git a/net/core/dst.c b/net/core/dst.c index 764bccb..8283158 100644 --- a/net/core/dst.c +++ b/net/core/dst.c @@ -235,6 +236,8 @@ again: static inline void dst_ifdown(struct dst_entry *dst, struct net_device *dev, int unregister) { + struct neighbour *neigh; + if (dst->ops->ifdown) dst->ops->ifdown(dst, dev, unregister); @@ -245,14 +248,13 @@ static inline void dst_ifdown(struct dst_entry *dst, struct net_device *dev, dst->input = dst_discard_in; dst->output = dst_discard_out; } else { - dst->dev = &loopback_dev; - dev_hold(&loopback_dev); - dev_put(dev); - if (dst->neighbour && dst->neighbour->dev == dev) { - dst->neighbour->dev = &loopback_dev; - dev_put(dev); - dev_hold(&loopback_dev); + neigh = dst->neighbour; + if (neigh && neigh->dev == dev) { + dst->neighbour = NULL; + neigh_release(neigh); } + dst->dev = NULL; + dev_put(dev); } } -- MST - To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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